Bug45: Search engine results for ChronoZoom have no description

Search results in Bing and Google for ChronoZoom return:
   - Bing: Empty
   - Google: A description for this result is not available because of this site's robots.txt
robots.txt is blocking everything, including cz.html.

Allowing all root .htm (but not specific timelines, exhibits, etc.) to be indexed by crawlers.